III–V colloidal nanocrystals: control of covalent surfaces

Kim, Young‐Sik; Chang, Jun; Choi, Hyekyoung; Kim, Yong Hyun; Bae, Wan Ki; Jeong, Sohee

doi:10.1039/c9sc04290c

Cited by 90 publications

(93 citation statements)

References 88 publications

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“…Colloidal quantum dots (QDs) are materials synthesized using wet chemistry, whose optical and physical properties are controlled by their size and shape due to quantum confinement effects. In particular, the freestanding colloidal QDs allow solution-based chemical post-processing and solution processable thin-film assembly 1 , 2 . As a result, colloidal QDs have attracted attention in various optoelectronic fields such as bio-imaging, displays, flexible devices, and stretchable devices 3 – 6 .…”

Section: Introductionmentioning

confidence: 99%

“…Chalcogenide colloidal QDs such as PbS, CdSe have been successfully applied to many fields as their synthetic methods were extensively developed, providing a targeted wavelength with high size uniformity 7 – 11 . Meanwhile, colloidal synthesis of rather covalent colloidal QDs is lagging behind because of difficulties originating from limited control over precursor reactivity in solution 2 , 12 .…”

Section: Introductionmentioning

confidence: 99%

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Diffusion dynamics controlled colloidal synthesis of highly monodisperse InAs nanocrystals

2021

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Highly monodisperse colloidal InAs quantum dots (QDs) with superior optoelectronic properties are promising candidates for various applications, including infrared photodetectors and photovoltaics. Recently, a synthetic process involving continuous injection has been introduced to synthesize uniformly sized InAs QDs. Still, synthetic efforts to increase the particle size of over 5 nm often suffer from growth suppression. Secondary nucleation or interparticle ripening during the growth accompanies the inhomogeneity in size as well. In this study, we propose a growth model for the continuous synthetic processing of colloidal InAs QDs based on molecular diffusion. The experimentally validated model demonstrates how precursor solution injection reduces monomer flux, limiting particle growth during synthesis. As predicted by our model, we control the diffusion dynamics by tuning reaction volume, precursor concentration, and injection rate of precursor. Through diffusion-dynamics-control in the continuous process, we synthesize the InAs QDs with a size over 9.0-nm (1Smax of 1600 nm) with a narrow size distribution (12.2%). Diffusion-dynamics-controlled synthesis presented in this study effectively manages the monomer flux and thus overcome monomer-reactivity-originating size limit of nanocrystal growth in solution.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Diffusion dynamics controlled colloidal synthesis of highly monodisperse InAs nanocrystals

2021

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“…Trap states in InAs semiconductors originate from surface In and As dangling bonds 20 . Growing epitaxially-matched inorganic shells on CQDs passivates surface defects, but it hinders CQD coupling and carrier transport 21,22 .…”

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confidence: 99%

“…Sn 2 S 6 4− and In 2 Se 4 2− ) enhances carrier mobility in III-V CQD solids, leading to an impressive mobility of 15 cm 2 V -1 s -1 , but introduces undesired in-gap states 19,23 . Etching As sites using strong acids facilitates In-site passivation but leads to low mobility (10 -3 cm 2 V -1 s -1 ) 18,20,24 .…”

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confidence: 99%

“…Considering the presence of DMF, its potential interactions with the passivants and the sixfold coordination of In, we calculated the stabilization energy of Br -/DMF and In-Br/DMF co-passivants. In the case of zinc-blende InAs structure, there are 1.5 DBs (electrons from As or holes from In) at (100) surfaces and 0.75 DBs at (111) surfaces 20 . These sites are hard to passivate as the ligands can only provide an integer number of carriers.…”

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Sub-nanosecond Infrared Photodetection using III-V Colloidal Quantum Dots

Sun¹,

Najarian²,

Zheng³

et al. 2020

Preprint

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Colloidal quantum dots (CQDs) are promising materials for IR light detection due to their tunable bandgap and solution processing; but to date, the time response of CQD IR photodiodes has been inferior to that provided by Si and InGaAs. We reasoned that the high permittivity of II-VI CQDs leads to slow charge extraction due to screening and capacitance; whereas III-Vs – if their surface chemistry could be mastered – offer a strong covalent character for low permittivity and fast operation. In initial studies, we found that existing covalent character led to imbalanced charge transport in InAs, the result of unpassivated surfaces and uncontrolled heavy doping. We report surface management using amphoteric ligand coordination and find that it addresses simultaneously the In and As surface dangling bonds. The new InAs CQD solids combine high mobility (0.04 cm2 V-1 s-1) with a 4x reduction in permittivity compared to PbS CQDs. The resulting photodiodes achieve a response time faster than 300 ps – a more than 100x improvement compared to the best previously-reported CQD photodiodes – combined with an external quantum efficiency (EQE) of 30% at 940 nm.

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Synthesis of NIR/SWIR Absorbing InSb Nanocrystals Using Indium(I) Halide and Aminostibine Precursors

Kwon,

Yeromina,

Cavallo

et al. 2024

Adv Funct Materials

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Colloidal InSb quantum dots (QDs) are a potential alternative to toxic Pb‐ and Hg‐chalcogenide QDs for covering the technologically important near‐infrared/shortwave infrared (NIR/SWIR) spectral range. However, appropriate Sb precursors are scarce and obtaining narrow size distributions is challenging. Tris(dimethylamido)antimony (Sb(NMe2)3) is an appealing choice due to its commercial availability and non‐pyrophoric character but implies the reduction of antimony from the +3 to the required –3 state. In reported works, strong reducing agents such as lithium triethylborohydride are used, which lead to the fast co‐reduction of both Sb3+ and In3+. The downsides of this approach are reproducibility issues and the risk of forming metal nanoparticles due to the different reduction kinetics of Sb3+ and In3+. Here, indium(I) halides are explored as simultaneous indium source and mild reducing agent for the antimony precursor. The wavelength of the excitonic absorption peak of the phase‐pure InSb QDs obtained with this approach can be tuned from 630 to 1890 nm, which corresponds to a size range of ≈2–7 nm. The synthesis can also be conducted in a heat‐up manner, which facilitates the scale‐up and paves the way for the use of InSb QDs in applications such as NIR/SWIR photodetectors, cameras, biological imaging, and telecommunications.

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III–V colloidal nanocrystals: control of covalent surfaces

Abstract: Unveiling the atomistic surface structure of colloidal quantum dots may provide the route to rational design of highly performing III–V nanocrystals with control over energy levels position, surface energy, trap passivation, and heterojunction interface.

Cited by 90 publications

References 88 publications

Diffusion dynamics controlled colloidal synthesis of highly monodisperse InAs nanocrystals

Diffusion dynamics controlled colloidal synthesis of highly monodisperse InAs nanocrystals

Sub-nanosecond Infrared Photodetection using III-V Colloidal Quantum Dots

Synthesis of NIR/SWIR Absorbing InSb Nanocrystals Using Indium(I) Halide and Aminostibine Precursors

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